Vol. xxiv] ENTOMOLOGICAL NEWS. 13 



atively phototropic, while others respond mainly only to one 

 stimulus and again others are unequally positively and nega- 

 tively phototropic. 



Culex pipiens, Culex aurifer, Culex canadensis, Culex syl- 

 vestris, Culex salinarius, Anopheles maculipennis and Wyeom- 

 yia smithii are negatively phototropic. They appear normally 

 only at night. They are also slightly positively phototropic 

 inasmuch as they are attracted to a certain extent by artificial 

 light and the low intensities found at dusk. In other words 

 these species are positively phototropic up to a certain inten- 

 sity of light, when they become negatively phototropic. 



Near the close of the season impregnated females of pi- 

 picns becomes strongly negatively phototropic and seek dark 

 hibernation quarters in spite of the warm temperatures, which 

 sometime prevail outside. Anopheles crucians, sometimes 

 called the daylight mosquito, is positively phototropic up to 

 the high intensity of light which occurs during the middle of 

 the day. Anopheles punctipennis responds both negatively 

 and positively, more so negatively. Its normal attraction is a 

 low intensity. 



Culex solUcitans seems to be equally negatively and posi- 

 tively phototropic, these tropic reactions evidently being de- 

 pendent upon nutrition, as it is difficult to find a more blood- 

 thirsty species. Culex perturbans is negatively phototropic 

 and cantator positively, but not to the extent of solUcitans'. 



Positive phototropism is most prevalent among the salt 

 marsh forms, Culex solUcitans, Culex cantator and Culex 

 taeniorhynchus all actingly positively but Culex salinarius, 

 which is also a salt marsh mosquito, responds negatively. 



Inasmuch as various factors influence phototropism, it 

 might be supposed that the positive reactions of solUcitans, 

 cantator and taeniorhynchus, all being biters of the first rank, 

 are dependent upon their desire for food. Positive photo- 

 tropism is not at all useful to mosquitoes inasmuch as it sub- 

 jects them to attacks by their natural enemies. 



